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Immunological-based diagnostic assays are important tools in detecting a variety of disease conditions. The effectiveness of these types of assays lies in part in the specificity of components within the immune system. Notwithstanding this specificity, immunological-based diagnostics are not necessarily always sensitive enough to detect low levels of innate and/or adaptive immune response activity, such as in response to a low grade infection or in the presence of a persistent low level infection or in subjects with active or latent disease states. There is a need to develop diagnostic assays with enhanced sensitivity in relation to cell-mediated immunoresponsiveness.
One form of immunological-based diagnostic assay involves the stimulation of T-cells with antigens or mitogens in either isolated cell culture or in whole blood culture followed by the detection of effector molecules such as cytokines produced by the stimulated T-cells (also referred to as effector T-cells). The effector molecules are generally detected using techniques such as enzyme immunoassays, multiplex head analysis, ELISpot and flow cytometry. Such assays are useful for detecting disease-specific T-cell responses. An example of a T-cell assay is QuantiFERON (Registered Trade Mark: Cellestis Limited). This is hereinafter referred to as “QFT” and is a test based on an Interferon-γ (IFN-γ) release assay (IGRA). Another assay employs the direct stimulation of highly purified human T-cells using anti-CD3 antibodies (a T-cell receptor agonist) and the Toll-like receptor (TLR) agonist, R848. However, not all effector molecules were detected and the assay is not suitable for whole blood.
The ability to quickly assess cell-mediated immunity and with a high degree of sensitivity is of clinical importance. A clinician needs to have an appreciation of the development of a disease state and its effect on the host's immune system.
There is a need, however, to improve the sensitivity of assays of cell-mediated immunoresponsiveness in a subject.